甲烷Methane

碳原子 sp³ 杂化，与四个氢形成等同的 C–H σ 键，键长 108.7 pm，H–C–H 键角 109.5°。分子高度对称，偶极矩为零，分子间只有很弱的色散力，所以沸点仅 −161.5 °C。C–H 键能约 439 kJ/mol，甲烷化学性质稳定，不与强酸、强碱和 KMnO₄ 反应。

Carbon is sp³ hybridised and forms four identical C–H σ bonds of 108.7 pm at 109.5°. The highly symmetric molecule has no dipole moment and only weak dispersion forces, so it boils at just −161.5 °C. With a C–H bond energy of about 439 kJ/mol, methane is chemically inert toward strong acids, strong bases and KMnO₄.

1776 年伏打在意大利马焦雷湖的沼泽中收集到可燃的“沼气”，并发现它与空气混合点燃会爆炸。1778 年前后他确认这是一种独立的气体。1866 年霍夫曼将其命名为 methane。煤矿中的甲烷（瓦斯）爆炸曾造成大量事故，1815 年戴维发明的安全灯大大减少了这类灾难。

In 1776 Volta collected flammable 'marsh air' from the reed beds of Lake Maggiore and found it exploded when mixed with air and ignited; by about 1778 he had identified it as a distinct gas. Hofmann named it methane in 1866. Methane explosions (firedamp) caused many coal-mine disasters until Davy's safety lamp of 1815 greatly reduced them.

甲烷是重要的燃料和化工原料：蒸汽重整制氢和合成气，进而合成氨、甲醇。甲烷 100 年尺度的全球变暖潜能值约为 CO₂ 的 28 倍，主要来自湿地、反刍动物、稻田、垃圾填埋和油气泄漏。

Methane is a major fuel and feedstock: steam reforming turns it into hydrogen and syngas for ammonia and methanol. Over 100 years its global-warming potential is about 28 times that of CO₂; it comes mainly from wetlands, ruminant livestock, rice paddies, landfills and oil and gas leaks.